if jami appears as a JACK client, then it is clearly implemented, at least partially - if the program behaves differently on different distros, then the distro maintainers would have the best answer as to why
generally, all questions regarding any software that you got from the repos of a distro, are best directed toward the distro maintainer - distro maintainers may choose to enable/disable different features, and yet, enabled features could be broken for other reasons, unrelated to the program itself; so the upstream devs are usually not the best people to ask, unless they also use that same distro regularly the arch package is maintained by the proaudio team - there is an arch-proaudio mailing list and the #archlinux-proaudio IRC channel on freenode the debian package is maintained by the debian-voip team - there is a pkg-voip-maintainers mailing list and the #debian-voip IRC channel on OFTC https://lists.archlinux.org/listinfo/arch-proaudio https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-voip-maintainers
